The larger type circular saws are provided with a series of recesses around their peripheries to receive teeth that are locked in place by retainers. The retainers have apertures for engagement by a suitable tool that operates the retainer for the insertion and removal of the teeth. Some of these retainers have a single aperture for receiving the tool and others have two apertures. A single aperture tooth is shown in Tower U.S. Pat. No. 2,651,219 and a double aperture tooth is shown in Bucknam U.S. Pat. No. 2,249,743.
These prior patents also illustrate devices that are used to sharpen circular saws and that are temporarily attached or mounted on the saw blade while sharpening is accomplished. The Tower patent includes a grinding motor mount that is positioned on the blade by engagement of a pin on the mount with an aperture in the retainer for the teeth.